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High-resolution Features in X-ray Binaries: What Do They Reveal?

Presentation #502.04 in the session Stellar/Compact IV.

Published onMay 03, 2024
High-resolution Features in X-ray Binaries: What Do They Reveal?

Changes in neutral Kα fluorescence lines and absorption column density, are often used as tracers of these changing physical conditions in X-ray binaries. These emission lines are ubiquitous to these systems and are powerful probes of the geometry and abundances of surrounding matter near the compact object. If the Compton optical depth of the medium is high (>0.1), the Fe Kα photon at 6.4 keV can be further Compton scattered in the same medium and lose some energy (~ 156 eV for backscattered photons). Such scattered photons produce a shoulder at a lower energy, known as the Compton Shoulder, and is most significant for the Fe Kα line due to its high fluorescence yield. These Compton scattering features at high energies provide a sensitive diagnostic for physical conditions of matter irradiated by an X-ray source such as an accretion disk/stellar wind structure illuminated by a compact object and can currently be exclusively studied only by Chandra gratings. We discuss the relevance of these features in High Mass X-ray Binaries like IGR J16318-4848, GX 1+4, and OAO 1657-415 and the importance of such high-resolution spectral studies with XRISM.

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